1. Field of the Invention
The invention relates to metallization process for manufacturing integrated circuit devices. More particularly, the invention relates to a method of performing integrated metallization using selective formation of a barrier layer for interconnect structures.
2. Description of the Background Art
Sub-half micron multilevel metallization is one of the key technologies for the next generation of very large scale integration (xe2x80x9cVLSIxe2x80x9d) for integrated circuits. The multilevel interconnections that lie at the heart of this technology require planarization of high aspect ratio apertures, including contacts, vias, lines or other features. Reliable formation of these interconnects is very important to the success of VLSI and to the continued effort to increase circuit density and quality on individual substrates and die.
Metallization, such as aluminum, when used at the contact level, requires a diffusion barrier between the aluminum and silicon. The diffusion barrier ensures that the aluminum does not diffuse into the silicon and interfere with the conductive characteristics of the structures in the silicon. Generally, the diffusion barrier is blanket deposited upon the integrated circuit structure and the aluminum is blanket deposited atop the diffusion barrier.
Additionally, to enhance performance, the barrier layer is fortified through oxygen stuffing. Such stuffing can cause the aluminum that is deposited atop the fortified barrier layer to have a rough surface and thus result in low reflectivity. High reflectivity (indicating good film morphology) is desirable to facilitate precise lithography of the metallization.
Therefore, a need exists in the art for a method of selective formation of a diffusion barrier such that aluminum is selectively deposited in a contact via.
The disadvantages associated with the prior art metallization processes are overcome by the present invention of a method of performing selective deposition of metal within a contact via. Specifically, the present invention forms a self-aligned silicide region by depositing titanium atop a structure containing contact vias, converting the titanium in the contact regions into silicide, removing the unreacted titanium, and performing nitridation of the titanium silicide to complete the formation of a barrier layer located in the contact region only. Once the barrier layer is formed, the layer can be optionally fortified through oxygen stuffing. Thereafter, the structure is metallized. Aluminum will grow upon the barrier layer such that selective growth occurs only in the vias. Metallization can also be accomplished by conventional chemical vapor deposition (CVD) of aluminum, an integrated CVD/PVD aluminum deposition process, or a conventional aluminum deposition, e.g., physical vapor deposition (PVD), followed by planarization.